Composite extensible member and method of manufacturing the same

ABSTRACT

An extensible composite member ( 1 ) including an extensible portion ( 10 ) having two sheet materials ( 2, 3 ) and elastic members ( 4 ) intermediate between the sheet materials. The two sheet materials ( 2, 3 ) are discontinuously bonded to each other in the extending direction of the extensible portion ( 10 ) (X direction) and a direction perpendicular thereto (Y direction). The elastic members ( 4 ) are arranged in the extensible portion ( 10 ) avoiding joints ( 5 ) between the sheet materials and have both ends thereof fixed to the sheet materials. Each of the two sheet materials ( 2, 3 ) forms folds ( 6 ) continuously running across a plurality of the elastic members ( 4 ).

TECHNICAL FIELD

The present invention relates to an extensible composite member and amethod of making the same.

BACKGROUND ART

In the field of absorbent articles including disposable diapers andsanitary napkins, it is a practice widely adopted to bond an elasticmember in its stretched state to a sheet material and allow the elasticmember to contract thereby to make gathers (an extensible portion with alarge number of folds) of the sheet.

JP-A-2001-11769 (reference-1) discloses an elastically extensible sheethaving a flat sheet material accordion-folded to make a large number offolds and elastic members bonded to the top of a plurality of the folds.

Japanese Utility Model 2518953 (reference-2) discloses a disposablediaper having an elastically extensible portion having a sheet materialof nonwoven fabric folded back into two layers and an elastic membersandwiched between the two layers. The sheet material is joined toitself along linear joints extending in a direction perpendicular to theextending direction of the elastic member, and the elastic member isbonded to the sheet material at the joints.

DISCLOSURE OF THE INVENTION

The folds of conventional general gathers have a short length in thedirection perpendicular to the extending direction, and the appearanceis not so neat.

The sheet of reference-I has each fold crossing a plurality of theelastic members and is relatively pleasant to the eye. However, the feelto the touch of the folds is not so good on account of the jointsbetween the sheet material and the elastic members.

The elastically extensible portion described in reference-2 is not verysoft in the direction parallel with the linear joints between the sheetmaterial layers due to the joints and therefore leaves room forimprovement in softness and feel to the skin.

The present invention provides, in its first aspect, an extensiblecomposite member having an extensible portion composed of two sheetmaterials and a plurality of elastic members disposed between the sheetmaterials. The two sheet materials are discontinuously bonded to eachother in the extending direction of the extensible portion and adirection perpendicular thereto. The elastic members are arranged in theextensible portion avoiding the joints between the sheet materials andhave both of their ends fixed to the sheet materials. Each of the twosheet materials forms a plurality of folds continuously running across aplurality of the elastic members.

The present invention also provides, in its second aspect, a method ofmaking the extensible composite member. The method includes the step ofarranging a plurality of elastic members in their stretched state on afirst sheet material and superposing a second sheet material on the sideof the first sheet material having the elastic members on, the step ofpartly joining the first and second sheet materials in their superposedstate in an area where the elastic member is absent, the step ofsubjecting the first and the second sheet materials with the elasticmembers there between to a process for fixing the elastic members to thefirst and the second sheet materials along places spaced apart from eachother in the extending direction of the elastic members, and the step ofallowing the elastic members to contract to cause each of the first andthe second sheet materials to form a plurality of folds.

The present invention provides, in its third aspect, an extensiblecomposite member composed of two sheet materials and a plurality ofelastic members disposed between the sheet materials. The two sheetmaterials are discontinuously bonded to each other in the extendingdirection of the elastic members and a direction perpendicular theretoto form joint lines each composed of joints in each of the twodirections. At least two of the elastic members are each disposed tooverlap each of the joints composing the joint line in the extendingdirection and fixed between the sheet materials at the individualjoints. The sheet materials each form folds between the joint lines inthe direction perpendicular to the extending direction.

The present invention provides, in its fourth aspect, a method of makingthe extensible composite member of the third aspect. The method includesthe steps of disposing a plurality of elastic members in their stretchedstate between two sheet materials and partly heat-pressing thesuperposed sheet materials with a plurality of projections to partlyfusion bond the sheet materials to form the above-described joints. Thestep of partly heat-pressing is carried out in a manner that does notresult in cutting the elastic members.

The present invention provides, in its fifth aspect, an extensiblecomposite member having two sheet materials and a plurality of elasticmembers disposed between the sheet materials. The two sheet materialsare partly bonded to each other to form joints. The joints line up tomake joint lines in a direction crossing the extending direction of theelastic members. A part of the joint lines and another part of the jointlines are different in positions of their joints (making up each jointline) in a direction (Y direction) crossing the extending direction (Xdirection). Each of the elastic members is fixed between the sheetmaterials in at least part of the joints. The sheet materials each formfolds between every two adjacent joint lines.

The present invention provides, in its sixth aspect, a method of makingthe extensible composite member of the fifth aspect. The method includesthe steps of disposing a plurality of elastic members in their stretchedstate between two sheet materials and partly heat-pressing thesuperposed sheet materials with a plurality of projections to partlyfusion bond the sheet materials to form the above-described joints. Thestep of partly heat-pressing is carried out in a manner that does notresult in cutting the elastic members.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of an extensible composite member according toan embodiment of the first aspect of the present invention, with a partcut away.

FIG. 2 is a plan of the extensible composite member of FIG. 1 with theextensible portion extended.

FIG. 3 illustrates an extensible composite member according to anotherembodiment of the first aspect of the present invention (correspondingto FIG. 2).

FIG. 4 illustrates extensible portions formed of the extensiblecomposite 10 members according to the first, the third, and the fifthaspects of the present invention, applied to a disposable diaper withfastening tapes.

FIG. 5 is a perspective of an extensible composite member according toan embodiment of the third aspect of the present invention, with a partcut away.

FIG. 6 is a plan of the extensible composite member of FIG. 5 with theelastic members extended to stretch flat.

FIG. 7 is a fragmentary cross-section of an embosser useful to make anextensible composite member of the types shown in FIGS. 5 and 10.

FIG. 8 illustrates an extensible composite member according to anotherembodiment of the third aspect of the present invention (correspondingto FIG. 6).

FIG. 9 illustrates an extensible composite member according to stillanother embodiment of the third aspect of the present invention(corresponding to FIG. 6).

FIG. 10 is a perspective of an extensible composite member according toan embodiment of the fifth aspect of the present invention, with a partcut away.

FIG. 11 is a plan of the extensible composite member of FIG. 10 with theelastic members extended to stretch flat.

FIG. 12 illustrates an extensible composite member according to anotherembodiment of the fifth aspect of the present invention (correspondingto FIG. 11).

FIG. 13(a) illustrates a pattern of arranging joints in still anotherembodiment of the fifth aspect of the present invention, in which thelongitudinal direction of the individual joints coincides with therunning direction of the joint lines.

FIG. 13(b) illustrates a pattern of arranging joints in still anotherembodiment of the fifth aspect of the present invention, in which thelongitudinal direction of the individual joints does not coincide withthe running direction of the joint lines.

FIG. 14 illustrates a pattern of arranging joints in still anotherembodiment of the fifth aspect of the present invention.

FIG. 15 illustrates a pattern of arranging joints in still anotherembodiment of the fifth aspect of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the first and the second aspects of the presentinvention will be described with reference to the accompanying drawings.As illustrated in FIG. 1, an extensible composite member 1 according toan embodiment (first embodiment) of the first aspect of the presentinvention has an extensible portion composed of two sheet materials 2and 3 and a plurality of elastic members 4 disposed between the twosheets.

The extensible portion 10 is formed in a central portion of theextensible composite member 1 in the elastic members 4 extendingdirection. The elastic members 4 are joined to the sheet materials atboth end portions 11 (only one of the end portions is shown) of theextensible composite member 1 in that direction.

As illustrated in FIG. 2, the two sheet materials 2 and 3 composing theextensible portion 10 are fusion bonded joined) to each otherdiscontinuously in both the extensible portion 10 extending direction (Xdirection) and a direction perpendicular thereto (Y direction).

In the first embodiment, the elastic members 4 are arranged parallel toeach other so as to extend in the longitudinal direction of theextensible composite member 1.

When elastic members are parallel with each other as in the presentembodiment, the extensible portion 10 extending direction is the same asthe elastic members 4 extending direction. When elastic members 4 arenot parallel with each other, the extensible portion extending directionis a direction perpendicular to the direction of folds (hereinafterdescribed) running across a plurality of elastic members.

FIG. 2 illustrates a pattern of forming fusion bonded parts joints)between the two sheet materials 2 and 3. As illustrated, in the firstembodiment, the fusion joints 5 are in a staggered pattern.

In order to assure formation of folds 6 continuously extending across aplurality of the elastic members 4, it is preferred that the fusionjoints 5 be arranged at a pitch P1 (see FIG. 2) of 1 to 30 mm, morepreferably 6 to 20 mm, in the extensible portion 10 extending direction(X direction) with the extensible portion being in the extended state(the state presented in FIGS. 2 or 3); that the individual fusion joints5 have a length L1 (see FIG. 2) of 0.1 to 5 mm, more preferably 0.2 to1.5 mm in the same direction in the same state; and that the ratio ofthe pitch P1 to the length L1 (P1/L1) be in the range of from 1.1 to300, more preferably from 4 to 100.

It is preferred that the two sheet materials 2 and 3 not be joined toeach other in the extensible portion 10 at places except the fusionjoints 5.

Each of the elastic members 4 is arranged in the extensible portion 10avoiding the fusion joints 5 of the two sheet materials, and fixed tothe sheet materials 2 and 3 only at its ends. Both ends of the elasticmembers 4 are fixedly held in between the sheet materials 2 and 3 at therespective end portions 11 of the extensible composite member 1 (onlyone of the end portions 11 is depicted in the figures). The two endportions 11 may be formed as extensible end portions.

The fusion joints 5 of the sheet materials are arranged to line up (tomake sealing lines) in the extending direction of the extensible portion10 (X direction) and in a direction perpendicular thereto (Y direction).The fusion joints 5 lining in the perpendicular direction are placedevery two adjacent elastic members.

There is a region with no fusion joint 5 between a line of fusion joints5 in the extensible portion 10 extending direction (X direction) and anadjacent line of fusion joints 5. The region continuously extendsbetween the two end portions 11 (only one of which is shown) of theextensible composite member 1. The elastic member 4 is disposed but notfixed along that region. The positions of fusion joints 5 in a line inthe extensible portion extending direction (X direction) are shifted byhalf pitch (P1/2) from those in an adjacent line.

When the extensible composite member 1 of the first embodiment is in arelaxed state (with no external force applied), the elastic members 4contract. As a result, the two sheet materials 2 and 3 each form aplurality of folds 6 continuously running across the elastic members 4.

The folds 6 of the sheets 2 and 3 project on the respective sides of theextensible composite member 1. Each fold 6 has a curved surface whosecross-section is arc-shaped at the top. The curved surface continues inthe Y direction perpendicular to the extensible portion extendingdirection. In the present embodiment, two folds 6 are created betweenevery two fusion joints 5 that are adjacent in the extensible portionextending direction (X direction). Every fold 6 continuously runs in theY direction perpendicular to the extensible portion extending directionwithout being cut at positions where it crosses the elastic members 4.

The extensible composite member 1 of the first embodiment has a verybeautiful appearance since a large number of the folds 6 created bycontraction of the elastic members 4 individually continue in thedirection (Y direction) perpendicular to the extensible portion 10extending direction. If the sheet materials 2 and 3 are continuouslyjoined (by, for example, fusion bonding or adhesion with an adhesive)along the elastic members 4, the folds 6, particularly the crest of thefolds 6, would be depressed where they overlap the elastic members 4,resulting in formation of random folds. Such randomness not only impairsneatness to the eye but also reduces freedom of deformation of the folds6 under external force, which reduces softness to the touch.

In the extensible composite member 1 of the first embodiment, theindividual elastic members 4 in the extensible portion 10 are presentbetween the valleys of every two adjacent folds 6 formed of the sheetmaterial 2 and the valleys of every two adjacent folds 6 formed of theother sheet material 4. The elastic members 4 are not bonded to thesevalleys of either the sheet material 2 or 3 as well as the other part ofthe sheet materials 2 and 3. Furthermore, the sheet materials 2 and 3are not continuously joined to each other in the extensible portion 10in either the extensible portion 10 extending direction or theperpendicular direction. Being so configured, the extensible compositemember 1 avoids an increase in stiffness and allows the folds 6 to bedeformed with more freedom under external force. Additionally, the foldshave a curved surface at the top. Therefore, the extensible compositemember 1 has an increased volume in the thickness direction and feelsextremely soft and pleasant when touched.

Since the elastic members in the extensible portion 10 are not fixed toeither the sheet material 2 or 3, the amount of an adhesive to be usedcan be minimized or reduced to zero. Particularly when the sheetmaterials 2 and 3 are joined together by fusion bonding as in thepresent embodiment, the effect in reducing the adhesive is outstanding.Reduction of a hot-melt adhesive assures breathability and moisturepermeability.

Materials making the extensible composite member 1 of the firstembodiment are described below.

Materials that can be used as the sheet materials 2 and 3 includenonwoven fabrics fabricated by various processes, such as air-throughnonwoven, heat-rolled nonwoven, hydroentangled nonwoven, spun-bondednonwoven, and melt-blown nonwoven, woven fabrics, knitted fabrics, resinfilms, and composite laminate sheets composed of two or more of thesesheet materials.

To create folds pleasant to the eyes and to the touch, it is desirableto use air-through nonwoven fabric, heat-rolled nonwoven fabric,hydroentangled nonwoven fabric, spun-bonded nonwoven fabric ormelt-blown nonwoven fabric as both the two sheet materials or at leastone of them, especially the one that is to come into direct contact withthe skin where the extensible composite member is designed to be appliedto the skin.

The sheets are deformed with the contraction of the elastic members toform folds. That is, the stiffness of the sheets is one of the factorsdecisive of the fold formability of the extensible composite member andthe cushioning properties of the folds formed. The stiffness of a sheetmaterial can be represented in terms of buckling strength.

The sheet material used in the present invention (inclusive of the firstto sixth aspects) preferably has a buckling strength of 100 cN or lower,more preferably 70 cN or lower. The buckling strength as referred toherein can be measured with a Tensilon universal tensile tester fromOrientec Corp. in compressive mode as follows.

Buckling Strength Testing Method (CD):

Test pieces measuring 150 mm in the machine direction (MD) and 30 mm inthe direction crossing the machine direction (CD) are cut out of asample and each formed into a 45 mm diameter cylinder by rolling. Theoverlapped ends were stapled together at their upper and lower parts tomake specimens. Measurement is taken with the Tensilon universal tensiletester in compressive mode under measuring conditions of a rate ofcompression of 10 mm/min and a measuring distance of 20 mm in ameasuring environment of 20° C. and 65% RH. The maximum strength of thespecimen when compressed by 20 mm is read for every specimen to obtainan average, which is taken as the buckling strength of the sample.

As stated, nonwoven fabric is a preferred sheet material. Nonwovenfabric as a sheet material preferably has a weight of 5 to 50 g/m², morepreferably 18 to 30 g/m². Nonwoven fabric having a weight in that rangepreferably has a buckling strength of 50 cN or lower, more preferably 30cN or lower, in the CD and of 70 cN or lower, more preferably 50 cN orlower, in the MD.

The material making the sheet material (e.g., fiber of nonwoven fabricor a film forming material of a resin film) preferably comprises a heatfusible resin, such as polyethylene and polypropylene. The fiberconstituting nonwoven fabrics can be sheath-core conjugate fibers havinga heat fusible resin only in the sheath.

The material of one of the two sheet materials and the material of theother sheet material may be the same or different.

The two sheet materials used in the present invention inclusive of thefirst to sixth aspects do not need to be separate sheets. A single sheetmaterial can be folded to make two facing panels, one of which serves asa first sheet material, and the other as a second sheet material.

Any known elastic materials of various kinds that have been used inabsorbent articles such as disposable diapers and sanitary napkins canbe used with no particular limitation as a material making the elasticmembers 4. Examples include synthetic rubbers such as styrene-butadiene,butadiene, isoprene and neoprene, natural rubber, EVA, stretchpolyolefins, and polyurethane. Forms of the elastic members include athread with a rectangular, square, circular or polygonal section, tape,or multifilamentous yarn.

Another factor decisive of fold formability of the extensible compositemember is a stretch ratio and a stretch stress of the elastic member.The elastic member is required to have a prescribed stretch ratio andstretch stress in order to create folds with a protruding cross-section.The elastic member is disposed between the sheet materials in astretched state at a stretch ratio preferably of 20% to 1000%, morepreferably 50% to 400%. On the elastic members' contracting, the excessof the nonwoven fabric in the portion having gathered protrudes outward,i.e., away from the fusion joints to form folds with a protrudentcross-section.

The height of the folds, which is of importance considering foldformability and cushioning properties, can be designed freely byselecting the pattern of arrangement and the pitch of the joints, thematerial, and the elastic members. The height of the folds is preferablyabout 1 to 15 mm per side. High folds can be created to provide anextensible composite member with a soft and voluminous hand feel byspacing the joints at a predetermined interval and by stretching theelastic members to a stretch ratio sufficient to gather the spacedjoints to form protrudent folds. In order to form folds with a height hon one side, the distance between adjacent joints is preferably 2×h atthe least. When the distance is the least (2×h), it is desirable for theelastic member to contract such that the adjacent joints come intocontact with each other.

Among preferred elastic members is a natural rubber (or syntheticrubber) member. A natural (or synthetic) rubber member is desirably alow modulus element having a thickness of 0.05 to 1.5 mm and a width of0.2 to 5 mm. A preferred stretch stress varies depending on thecross-sectional area. As a typical example, it is preferred to use amonofilament of 0.35 mm in thickness and 0.91 mm in width having astress at 100% elongation usually of about 1 to 70 g, preferably ofabout 1 to 40 g, more preferably of about 1 to 30 g. A plurality ofelastic members with such stress characteristics are used in theextensible composite member.

Also included in preferred elastic members is Spandex fiber (elasticpolyurethane fiber). A monofilamentous Spandex fiber having a finenesspreferably of 10 to 3360 denier, more preferably of 70 to 1120 denier,is used. “Denier” is a unit of thickness of a yarn. A yarn weighing onegram per 9,000 meters is one denier. A plurality of such Spandex elasticfibers are used at a stretch ratio of 30% to 500%.

An extensible composite member that softly extends and contracts and hasbeautiful folds can be obtained by disposing a plurality ofmonofilaments of the above-described low modulus elastic member at ahigh stretch ratio preferably of 100% or higher, more preferably of 200%or higher.

The aforementioned extensible composite member 1 is produced efficientlyand economically by, for example, the following method, which is anembodiment of the second aspect of the present invention.

A plurality of elastic members 4 are disposed parallel to each other intheir stretched state on a sheet material 2, and another sheet material3 is superposed on the elastic members side of the sheet material 2.

The sheet materials superposed on each other are fusion bonded in partsin a region where the elastic members 4 are absent by heat embossing,ultrasonic embossing or like means. Heat embossing or ultrasonicembossing is carried out by, for example, introducing the two sheetmaterials into the nip between an embossing roll having projections in apattern corresponding to the pattern of arrangement of the fusion joints(see FIG. 2) and a backup roll.

The two sheet materials having the elastic members 4 therebetween arethen subjected to a uniting process for fixing the elastic members 4 toboth the sheet materials 2 and 3 along portions spaced apart in theelastic members 4 extending direction. The uniting process is a processby which the elastic members are joined to both the sheet materials 2and 3 and includes heat embossing and ultrasonic embossing. The unitingprocess may be a process in which an adhesive is applied to one or bothof the two sheet materials and/or the elastic members and pressing theadhesive-applied parts. The adhesive is applied to, for example, thesheet material 2 before disposing the elastic members 4 thereon, or thesheet material 3 before being overlaid on the sheet 2, or the elasticmembers 4 before or after being disposed on the sheet material 2.

The sheet materials 2 and 3 with the elastic members 4 therebetween iscut across so that the portions having been subjected to the unitingprocess may be positioned at both ends of the cut part in the elasticmembers 4 extending direction. The elastic members 4 are let to contractto make each of the sheet materials 2 and 3 create folds. The extensiblecomposite member 1 having the above-described configuration is thusobtained.

Another embodiment (second embodiment) of the first aspect of thepresent invention in which an extensible composite member 1′ is providedwill then be described. The second embodiment will be illustrated withreference to differences from the first one. Elements identified withthe same numerals as in the first embodiment may be identical and willnot be redundantly described. To those particulars that are notdescribed here is applied the description of the extensible compositemember 1.

As shown in FIG. 3, in the extensible composite member 1′, fusion joints5 between the sheet materials 2 and 3 are arranged to line up in boththe extending direction of the extensible portion 10 (X direction) and adirection perpendicular thereto (Y direction). The fusion joints 5lining in the perpendicular direction are placed between every twoadjacent elastic members 4.

When the extensible composite member 1′ of the second embodiment is in arelaxed state (with no external force applied), the elastic members 4contract, whereby the two sheet materials 2 and 3 each gather to form aplurality of folds 6 continuously running across the elastic members 4similarly to the first embodiment. Thus, the extensible composite member1′ exerts the same action and effect as with the extensible compositemember 1.

In the second embodiment, one fold 6 is created between every two fusionjoints 5 that are adjacent in the extensible portion extending direction(X direction).

In order to assure formation of folds 6 continuously running across aplurality of the elastic members 4, it is preferred that the fusionjoints 5 be arranged at a pitch P2 (see FIG. 3) of 1 to 20 mm, morepreferably 3 to 10 mm, in the extensible portion 10 extending direction(X direction) with the extensible portion 10 being in the extendedstate; that the individual fusion joints 5 have a length L2 (see FIG. 3)of 0.1 to 5 mm, more preferably 0.2 to 1.5 mm in the same direction inthe same state; and that the ratio of the pitch P2 to the length L2(P2/L2) be in the range of from 1.1 to 200, more preferably from 2 to50.

In the above-illustrated extensible composite members 1 and 1′,especially the extensible composite member 1, it is preferred that thepitch P3 (see FIGS. 2 and 3) of the fusion joints 5 in the direction (Ydirection) perpendicular to the extensible portion 10 extendingdirection be 1 to 40 mm, more preferably 2 to 15 mm; that the length L3(see FIGS. 2 and 3) of the individual fusion joints 5 be 0.5 to 20 mm,more preferably 1 to 10 mm in that direction; and that the ratio of thepitch P3 to the length L3 (P3/L3) be in a range of from 1.05 to 80, morepreferably of from 1.05 to 15.

The third and fourth aspects of the present invention will be describedbased on their preferred embodiments by way of the drawings.

FIGS. 5 and 6 illustrate an extensible composite member 1A according toan embodiment of the third aspect of the present invention. As shown,the extensible composite member 1A is composed of two sheet materials 2and 3 and a plurality of elastic members 4 disposed therebetween.

The extensible composite member 1A is rectangular in its plan view. Theextensible composite member 1A has an end seal 11 at both ends thereof(only one end is illustrated) in the extending direction of the elasticmembers 4 (i.e., the direction of arranging each elastic member 4), eachend seal 11 being continuous in the direction perpendicular to theelastic members 4 extending direction. All the elastic members 4 arefixed between the sheet materials 2 and 3 in the end seals 11. Theportion of the extensible composite member 1A except the end seals 11 isan extensible portion 10.

As illustrated in FIG. 6, the sheet materials 2 and 3 arediscontinuously fusion bonded joined) to each other in both theextending direction of the elastic members 4 (X direction) and adirection perpendicular to that direction (Y direction). “Directioncrossing the extending direction of the elastic members 4” as will bereferred to herein denotes a direction unparallel with the extendingdirection of the elastic members 4, making a certain angle with theextending direction. In this particular embodiment, the crossingdirection is a direction perpendicular to the extending direction, i.e.,Y direction. The crossing angle being taken as 90° when the crossingdirection is perpendicular to the elastic members 4 extending directionas in the present embodiment, the crossing direction preferably makes anangle of 75° to 105°, more preferably 85° to 95°, even more preferably90°.

In the present embodiment, the elastic members 4 are arranged parallelto each other. When elastic members are parallel with each other, thedirection of extension (stretch) and contraction of the elastic members4 is the same as the running direction of the elastic members 4. Whenelastic members 4 are not parallel with each other, the elastic members4 extending and contracting direction is a direction perpendicular tothe running direction of folds 6 (hereinafter described).

As illustrated in FIG. 6, the extensible composite member 1A has aplurality of (seven in the embodiment illustrated) joint lines 50, onlyone of which is indicated by numeral 50, each of which includes aplurality of fusion joints 5 lining up in the elastic members 4extending direction (X direction). It also has a plurality of jointlines 51, only one of which is indicated by numeral 51, each of whichincludes a plurality of fusion joints 5 lining up in the directionperpendicular to the elastic members 4 s extending direction (Ydirection).

The joint lines 50 in the elastic members 4 extending direction (Xdirection) are parallel to each other. So are the joint lines 51 in thedirection perpendicular to the extending direction (Y direction). Thereis a region with no fusion joint 5 between every two fusion lines 50 inthe X direction. The region continuously extends between the two endseals 11 (only one of which is shown) of the extensible composite member1A.

It is preferred for improving softness that the joint lines in adirection crossing the elastic members 4 extending direction (Ydirection in the case of the present embodiment) each have a ratio of apitch P11 (see FIG. 6) of arranging the fusion joints 5 to a length L11(see FIG. 6) of the individual fusion joints (P11/L11) ranging from 1.05to 80, more preferably 1.05 to 15, and that the pitch P11 of arrangingthe fusion joints be from 1 to 40 mm, more preferably 2 to 15 mm.

From the same viewpoint, the length L11 is preferably 0.5 to 20 mm, morepreferably 1 to 10 mm, and the length L12 (see FIG. 6) between theadjacent fusion joints in that joint line is preferably 0.5 to 30 mm,more preferably 1 to 20 mm.

In order to assure formation of folds 6, especially folds 6 continuouslyrunning across a plurality of the elastic members 4 and thereforebeautiful to the eye, it is preferred that the fusion joints 5 bearranged at a pitch P12 (see FIG. 6) of 1 to 30 mm, more preferably 2 to15 mm, in a joint line along the elastic members 4 extending direction(X direction); that the individual fusion joints 5 have a length L1 3(see FIG. 6) of 0.1 to 5 mm, more preferably 0.2 to 1.5 mm in thatdirection; and that the ratio of the pitch P12 to the length L13(P12/L13) be in the range of from 1.1 to 300, more preferably from 4 to100.

The above-recited dimensions and ratios are measured with the extensiblecomposite member being in a stretched flat state by stretching theelastic members (a state in which the extensible composite member isstretched out to the same dimension as reached when it is flattened withany influences of the elastic members excluded by, for example, cuttingthe elastic members) as illustrated in FIG. 6.

In the present embodiment, all the elastic members 4 are each disposedto overlap every fusion joint 5 forming a joint line 50 in the elasticmembers 4 extending direction (X direction). Each elastic member 4passes the middle of the individual fusion joints 5 in the Y directionand fixed between the sheet materials 2 and 3 at each fusion joint 5without being cut at the fusion joints 5.

When the extensible composite member 1A of the present embodiment is ina relaxed state (with no external force applied), the elastic members 4contract, whereby the two sheet materials 2 and 3 each form a pluralityof folds 6 between every two adjacent joint lines in the directioncrossing the elastic members 4 extending direction (Y direction) asshown in FIG. 5.

The folds 6 of the sheets 2 and 3 project on the respective sides of theextensible composite member 1A. Each fold 6 has a curved surface whosecross-section is arc-shaped at the top. Every fold 6 continuously runsin the perpendicular direction (Y direction) across the elastic members4 without being cut at positions where it crosses the elastic members 4.Therefore, the folds 6 are very beautiful to the eye.

Since the elastic members 4 are fixed between the sheet materials 2 and3 at the fusion joints 5 forming the joint lines 50 along the elasticmembers 4 extending direction (X direction), the contracting stress ofthe elastic members 4 is used to securely gather the two sheet materialsbetween every two adjacent fusion joints in every joint line 50.Therefore, uniformity that is not to be impaired can be achieved amongthe folds 6 formed. Moreover, since the joint lines 51 along thedirection crossing the elastic members 4 extending direction (Ydirection) are each formed of spacedly arranged fusion joints 5, theextensible composite member 1A is very soft and flexibly deformable by,for example, a force compressing the extensible composite member 1A inthe Y direction or a force curving the extensible composite member 1Aalong the Y direction. Therefore, where the extensible composite member1A is used in an absorbent article as a member making gathers (anextensible portion with a large number of folds), particularly as amember forming standing gathers (standing anti-leak cuffs), the gathersare soft and pleasant to the touch and less irritating to the skin.

In the extensible composite member 1A of the present embodiment, theindividual elastic members 4 are present between the valleys of everytwo adjacent folds 6 formed of the sheet material 2 and the valleys ofevery two adjacent folds 6 formed of the other sheet material 3.Additionally, the folds have a curved surface at the top. Therefore, theextensible composite member 1 A has an increased volume in the thicknessdirection and feels extremely soft and pleasant when touched.

Materials that can be used to make the elements constituting theextensible composite member 1A include those described with respect tothe extensible composite member 1. Unless inconsistent with the context,the description of the materials making the extensible composite memberof the first aspect of the invention applies to the extensible compositemember of the third aspect.

In the present embodiment, too, the sheet materials 2 and 3 are deformedwith the contraction of the elastic members 4 to form folds 6. Similarlyto the extensible composite member 1, the stiffness of the sheetmaterials 2 and 3 is an important factor decisive of the foldformability of the extensible composite member and the cushioningproperties of the folds formed, and another factor decisive of the foldformability of the extensible composite member is a stretch ratio and astretch stress of the elastic members. The preferred constitution of theextensible composite member 1 explained above in connection with thesefactors (e.g., the buckling strength of the sheet materials, the stretchof the elastic members when disposed between the sheet materials, andthe height of the folds) also applies to the extensible composite member1A.

Where nonwoven fabric is chosen as a sheet material, it is preferred touse nonwoven fabric having a weight of 5 to 50 g/m², more preferably 8to 30 g/m². Nonwoven fabric having a weight in that range preferably hasa buckling strength of 50 cN or lower, more preferably 30 cN or lower,in the CD and of 70 cN or lower, more preferably 50 cN or lower, in theMD. To use such soft sheet materials secures fold formability.

The aforementioned extensible composite member 1A is producedefficiently and economically by, for example, the following method.

A plurality of elastic members 4 are disposed in their stretched statebetween two sheet materials 2 and 3 to prepare a laminate 12 in whichthe two sheet materials are not joined together. The laminate 12 ispartly fusion bonded by heat-pressing with projections 7 arranged in thepattern of fusion joints 5 (see FIG. 6) as illustrated in FIG. 7. Careshould be taken not to cut the elastic members 4 in the partial heatpressing. In order for the two sheet materials to be fusion bondedtogether and, at the same time, for the elastic members 4 to be fusionbonded, without being cut, to the sheet materials via the heat fusiblefiber present in the sheet materials, it is preferred to create optimumconditions by controlling three parameters: (1) pressing pressure of theprojections 7 to the anvil roll 71, (2) clearance between theprojections 7 and the anvil roll 71, and (3) temperature of theprojections 7 and the anvil roll 71. It is also effective for preventingthe elastic members from being cut to select a material unsusceptible tothe influences of pressure and heat, i.e., a cutting-resistant materialas elastic members and to set the stretch ratio of the elastic membersrather low as the product specification.

It is possible to positively reduce the pressure imposed to the elasticmembers. Means for reducing pressure application include measures toavoid pressure application to where the projections 7 cross the elasticmembers. For example, the anvil roll receiving the projections may bemade of rubber, e.g., silicon rubber. Where durability of rubber is aproblem, rubber may be applied only to the parts on which the elasticmembers are pressed. Another example is to use projections each having agroove (depression) 72 for pressing pressure reduction along where theelastic member 4 is disposed. Heat fusion using such projections can beeffected, e.g., with a heat embosser or an ultrasonic embosser byintroducing the laminate 12 into the nip between an embossing roll 70with the projections 7 on its peripheral surface and a facing anvil roll(backup roll) 71.

The embosser illustrated in FIG. 7 additionally has grooves(depressions) 73 for pressing pressure reduction on the peripheralsurface of the anvil roll 71, on which the laminate 12 is pressed underthe projections 7, along where the elastic members are present.

By making a groove 72 and/or grooves 73 for pressing pressure reductionon the projections for fusion bonding and/or the facing surface, theelastic members 4 can easily be fixed in the fusion joints 5 withoutbeing cut. The parts of the elastic member 4 in the fusion joint 5 maybe merely held between the two sheet materials but with tightness so asnot to move between the two sheet materials or may have the surfacethereof fusion bonded to one or both of the sheet materials. The groovesfor pressing pressure reduction can be provided on either one or both ofthe projections and facing surface.

In a preferred mode, grooves for pressing pressure reduction areprovided not on the projections of the embossing roll but on the anvilroll only. A sheet is introduced along the surface of the anvil roll,and the elastic members 4 are introduced along the anvil roll via thesheet so that they may fit in the respective grooves for pressingpressure reduction. Fusion bonding is performed with the elastic memberspositioned in the grooves so as not to move in the CD. That is, with thesheet being wrapped around the anvil roll, the elastic members areplaced along the position of the grooves. By so doing, high positioningprecision in the CD can be achieved in sealing the two sheet materialsby pressing with the projections across the grooves on the anvil roll.Achievement of high positioning precision provides freedom of design ofthe seal pattern, making it feasible to produce a more fit-to-useextensible composite material.

The depth of the groove for pressure reduction is suitably such that theelastic member sandwiched between the sheet materials in the stretchedstate may fit into the groove. Where the elastic member fits neatly intothe groove, the sheet materials can be heat sealed at positions on eachside of the elastic member without damaging the elastic member. Tightfit of the elastic member provides resistance against the elasticmember's contraction and keeps the elastic member in the positionwithout allowing the elastic member toget out of position. When thegroove is shallow, heat sealing is accompanied by damage to the elasticmember. In this situation, although there is a possibility that theextension and contraction capabilities of the elastic member is reduced,positioning of the elastic member is further ensured because the elasticmember is fusion bonded inclusively together with the two sheetmaterials.

While the above-described positioning method has been explained withreference to the third and fourth aspects, the same effects are producedwhen applied to the fifth and sixth aspects of the invention. Whenapplied to the first and second aspects, the positioning method is alsoadvantageous. For example, the positioning method makes it possible toform gathers stably even when a distance between lines of seals, viewedin the CD, is reduced, which enables reduction of the distance indesigning the folds formed between lines of seals.

After the fusion joints 5 are formed, the two sheet materials having theelastic members 4 therebetween are subjected to a uniting process forforming the end seals 11 along portions spaced apart in the elasticmembers 4 extending direction. The uniting process is accomplished byheat embossing or ultrasonic embossing. The uniting process may be aprocess in which an adhesive is applied to one or both of the two sheetmaterials and/or the elastic members and the adhesive-applied parts ispressed. When end seals 11 are not formed, the uniting process can beomitted.

The sheet materials 2 and 3 with the elastic members 4 therebetween isthen cut across along such positions that the portions having beensubjected to the uniting process may be positioned at both ends of thecut part in the elastic members 4 extending direction. The elasticmembers 4 are let to contract to make each of the sheet materials 2 and3 create folds. The extensible composite member 1A having theabove-described configuration is thus obtained. Where, as in theextensible composite member 1C shown in FIG. 9, an extensible compositemember has elastic members 4B that do not pass through the fusion joints5, the uniting process is particularly preferred to fix the ends of suchelastic members.

The fifth and sixth aspects of the present invention will be describedbased on their preferred embodiments by referring to the accompanyingdrawings.

An extensible composite member ID as an embodiment of the fifth aspectis composed of two sheet materials 2 and 3 and a plurality of elasticmembers 4 disposed therebetween as illustrated in FIGS. 10 and 11.

The extensible composite member ID is rectangular in its plan view. Theextensible composite member ID has an end seal 11 at both ends thereof(only one end is illustrated) in the extending direction (runningdirection) of the elastic members 4, each end seal 11 being continuousin the direction perpendicular to the elastic members 4 extendingdirection. All the elastic members 4 are fixed between the sheetmaterials 2 and 3 in the end seals 11. The portion of the extensiblecomposite member ID is except the end seals 11 is an extensible portion10.

As illustrated in FIG. 11, the sheet materials 2 and 3 are partly joinedtogether by fusion bonding to form a plurality of joints 5. The joints 5line up to form a plurality of joint lines (S1 to S8) running in adirection (direction Y) crossing the elastic members 4 extendingdirection (X direction). In this embodiment, each of the joint lines S1to S8 is made up of a plurality of joints (a group of joints) spacedlyplaced in the Y direction.

“Direction crossing the elastic members 4 extending direction” as usedherein denotes a direction unparallel with the extending direction ofthe elastic members 4, making a certain angle with the extendingdirection. In this particular embodiment, the crossing direction is adirection perpendicular to the elastic members 4 extending direction,i.e., Y direction. The crossing angle being taken as 90° when thecrossing direction is perpendicular to the elastic members 4 extendingdirection as in the present embodiment, the crossing directionpreferably makes an angle of 75° to 105°, more preferably 85° to 95°,even more preferably 90°. FIGS. 13(a) and 13(b) present other examplesof joint lines running in a direction crossing the elastic members 4extending direction. The joint lines extending in a direction crossingthe elastic members 4 extending direction may coincide with thelongitudinal direction of the individual joints making up each jointline as in the example shown in FIG. 13(a) or may have an angle with thelongitudinal direction of the individual joints 5 making up each jointline as in the example of FIG. 13(b).

In the present embodiment, the elastic members 4 are equally spaced andparallel to each other. When elastic members are parallel with eachother, the direction of extension (stretch) and contraction of theelastic members 4 is the same as the running direction of the elasticmembers 4. When elastic members 4 are not parallel with each other, theelastic members 4 extending and contracting direction is a directionperpendicular to the running direction of folds 6 (hereinafterdescribed).

As illustrated in FIG. 11, the extensible composite member ID has aplurality of (eight in the embodiment illustrated) joint lines S1 to S8,each composed of a plurality of fusion joints 5, spacedly formed in theelastic members 4 extending direction (X direction). In FIG. 11, onlyone of the joint lines is indicated by a dashed line. The joint linesare equally spaced and parallel with each other. The joints making upeach joint line are equally spaced in the Y direction. In the presentembodiment, all the joint lines are equal in the shape and the size ofthe individual joints and the pitch P11 of the joints per joint line.

As shown in FIG. 11, a part of the joint lines S1 to S8 (specifically,S1 and S6) and another part of the joint lines (specifically, S2 to S5,S7, and S8) are different in positions of the joints 5 making up eachjoint line in a direction (Y direction) crossing the extending direction(X direction).

Specifically, the positions of the joints composing a joint line in thedirection (Y direction) crossing the elastic members 4 extendingdirection (X direction) change from one end (the left end in FIG. 11) tothe other end (the right end in FIG. 11) in the extending direction (Xdirection).

More specifically, the positions of the joints composing a joint line inthe direction (Y direction) crossing the extending direction (Xdirection) vary from one end to the other in the elastic members 4extending direction (X direction) by a given distance in the Ydirection.

As shown in FIG. 11, the joints 5 of the joint line SI and those of thejoint line S2 are relatively shifted in the direction (Y direction)crossing the extending direction by a distance L4. The same relationshipapplies to every two adjacent joint lines.

In the present embodiment, every fifth joint line has the joints at thesame positions in the Y direction. That is, each pair in the joint linesS1 and S6, the joint lines S2 and S7, and the joint lines S3 and S8 havetheir joints at the same positions. A plurality of joint lines differentfrom each other in the positions of the joints in the Y direction areformed in such an arrangement that joint lines having their joints atthe same positions in Y the direction may appear at every plurality ofjoint lines (e.g., 2 to 10 joint lines). By arranging the joints atpositions shifted by a constant distance, the extensible compositemember has a neat appearance, and the stress of the elastic members canbe equally applied to each of the two sheet materials.

The distance L4, an amount of displacement of the joints betweenadjacent joint lines, varies depending on the length of the individualjoints but is preferably in a range of from 3% to 50%, more preferablyfrom 5% to 30%, of the pitch P11 of the joints in a joint line from thestandpoint of a good visual appeal and equal application of thecontraction stress.

To obtain improved flexibility, the ratio of the pitch P11 (see FIG. 11)of the fusion joints 5 in each of the joint lines S1 to S8 to the lengthL11 (see FIG. 11) of the individual fusion joints 5, P 11/L11,preferably ranges from 1.05 to 80, more preferably from 1.05 to 15, andthe pitch P11 of the fusion joints is preferably 1 to 40 mm, morepreferably 2 to 15 mm.

For the same purpose, it is preferred that the length L11 be 0.5 to 20mm, more preferably 1 to 10 mm, and that the distance L12 (see FIG. 11)between adjacent fusion joints be 0.5 to 30 mm, more preferably 1 to 20mm.

In order to form folds 6, especially folds 6 continuously running acrossa plurality of the elastic members 4 and having a good visual appeal, itis preferred that the joint lines have a pitch P12 (see FIG. 11) of 1 to30 mm, more preferably 2 to 15 mm and that the individual fusion joints5 have a length L13 (see FIG. 11) of 0.1 to 5 mm, more preferably 0.2 to1.5 mm, in the elastic members 4 extending direction (X direction). Forthe same purpose, the ratio of the pitch P12 to the length L13 (P12/L13)is preferably in the range of from 1.1 to 300, more preferably from 4 to100.

The above-recited dimensions and ratios are measured with the extensiblecomposite member being in a stretched flat state by stretching theelastic members (a state in which the extensible composite member isstretched out to the same dimension as reached when it is flattened withany influences of the elastic members excluded by, for example, cuttingthe elastic members) as illustrated in FIG. 11.

Each elastic member 4 is fixed between the sheet materials 2 and 3 at atleast a part of the joints 5.

In the present embodiment, every elastic member 4 is fixed between thesheet materials 2 and 3 at joints of a plurality of joint lines. Forexample, every elastic member 4 shown in FIG. 11 is disposed to overlapthe fusion joints 5 making up the joint lines S1 to S4 and the fusionjoints 5 making up the joint lines S6 to S8 and fixed between the sheetmaterials 2 and 3 at each of the overlapping joints 5 without being cutat these joints. The joint lines including the joints at which anelastic member is fixed may be different from the joint lines includingthe joints at which another elastic member is fixed.

Each elastic member 4 is fixed at the end seals 11 and the joints 5 inits stretched state. The stretch ratio or stretch stress may varybetween elastic members 4. For instance, in application as a waistgather band of a pull-on diaper, the elastic member closer to the waistopening (upper elastic member) can be designed to exert a strongerextension and contraction stress to prevent sliding down withoutimposing excessive constrictive pressure.

When the extensible composite member ID of the present embodiment is ina relaxed state (with no external force applied), the elastic members 4contract, whereby the two sheet materials 2 and 3 each form a pluralityof folds 6 between every two adjacent joint lines as shown in FIG. 10.

The folds 6 of the sheets 2 and 3 project on the respective sides of theextensible composite member ID. Each fold 6 has a curved surface whosecross-section is arc-shaped at the top. Every fold 6 continuously runsin the perpendicular direction (Y direction) across the elastic members4 without being cut at positions where it crosses the elastic members 4.Therefore, the folds 6 are very beautiful to the eye.

In the present embodiment, since the joint lines S1 to S8 along thedirection (Y direction) crossing the elastic members 4 extendingdirection are each formed of spacedly arranged fusion joints 5, theextensible composite member ID is very soft and flexible. It is flexiblydeformable by, for example, a force compressing the extensible compositemember ID in the Y direction or a force curving the extensible compositemember ID along the Y direction. Therefore, where the extensiblecomposite member ID is used in an absorbent article as a member makinggathers (an extensible portion with a large number of folds),particularly as a member forming standing gathers (standing leakproofcuffs), the gathers are soft and pleasant to the touch and lessirritating to the skin.

In the extensible composite member ID of the present embodiment, theindividual elastic members 4 are present between the valleys of everytwo adjacent folds 6 formed of the sheet material 2 and the valleys ofevery two adjacent folds 6 formed of the other sheet material 3.Additionally, the folds have a curved surface at the top. Therefore, theextensible composite member ID has an increased volume in the thicknessdirection and feels extremely soft and pleasant when touched.

The elastic members 4 used in the extensible composite member ID of thepresent embodiment are made of a material capable of developingcontraction stress uniformly. Accordingly, the contraction stress of theelastic members 4 can be used to securely gather the two sheet materialsbetween every two adjacent fusion joints. As a result, uniformity thatis not to be impaired can be achieved among the folds 6 formed.

Materials that can be used to make the elements constituting theextensible composite member ID include those described with respect tothe extensible composite member 1. Unless inconsistent with the context,the description of the materials making the extensible composite memberof the first aspect of the invention applies to the extensible compositemember of the fifth aspect.

In the present embodiment, too, the sheet materials 2 and 3 are deformedwith the contraction of the elastic members 4 to form folds 6. Similarlyto the aforementioned extensible composite member 1, the stiffness ofthe sheet materials 2 and 3 is an important factor decisive of the foldformability of the extensible composite member and the cushioningproperties of the folds formed, and another factor decisive of the foldformability of the extensible composite member is a stretch ratio and astretch stress of the elastic members. The preferred constitution of theextensible composite member 1 explained above in connection with thesefactors (e.g., the buckling strength of the sheet materials, the stretchof the elastic members when disposed between the sheet materials, andthe height of the folds) also applies to the extensible composite memberID.

Where nonwoven fabric is chosen as a sheet material, it is preferred touse nonwoven fabric having a weight of 5 to 50 g/m², more preferably 8to 30 g/m². Nonwoven fabric having a weight in that range preferably hasa buckling strength of 50 cN or lower, more preferably 30 cN or lower,in the CD and of 70 cN or lower, more preferably 50 cN or lower, in theMD. To use such soft sheet materials secures fold formability.

The above-illustrated extensible composite member ID is producedefficiently and economically by, for example, the following method.

A plurality of elastic members 4 are disposed in their stretched statebetween two sheet materials 2 and 3 to prepare a laminate 12 in whichthe two sheet materials are not joined together. The laminate 12 ispartly fusion bonded by heat pressing with projections 7 arranged in thepattern of fusion joints 5 (see FIG. 11) as illustrated in FIG. 7. Careshould be taken not to cut the elastic members 4 in the partial heatpressing. In order for the two sheet materials to be fusion bondedtogether and, at the same time, for the elastic members 4 to be fusionbonded to the sheet materials via the heat fusible fiber present in thesheet materials without being cut, it is preferred to create optimumconditions by controlling three parameters: (1) pressing pressure of theprojections 7 to the anvil roll 71, (2) clearance between theprojections 7 and the anvil roll 71, and (3) temperature of theprojections 7 and the anvil roll 71. It is also effective for preventingthe elastic members from being cut to select a material unsusceptible tothe influences of pressure and heat, i.e., a cutting-resistant materialas elastic members and to set the stretch ratio of the elastic membersrather low as the product specification.

It is possible to positively reduce the pressure imposed to the elasticmembers. Means for reducing pressure application include measures toavoid pressure application to where the projections 7 cross the elasticmembers. For example, the anvil roll receiving the projections may bemade of rubber, e.g., silicon rubber. Where durability of rubber is aproblem, rubber may be applied only to the parts on which the elasticmembers are pressed. Another example is to use projections each having agroove (depression) 72 for pressing pressure reduction along where theelastic member 4 is disposed. Heat fusion using such projections can beeffected, e.g., with a heat embosser or an ultrasonic embosser byintroducing the laminate 12 into the nip between an embossing roll 70with the projections 7 on its peripheral surface and a facing anvil roll(backup roll) 71.

The embosser illustrated in FIG. 7 additionally has grooves(depressions) 73 for pressing pressure reduction on the peripheralsurface of the anvil roll 71, on which the laminate 12 is pressed underthe projections 7, along where the elastic members are disposed.

By making grooves 72 and 73 for pressing pressure reduction on theprojections for fusion bonding and/or the facing surface, the elasticmembers 4 can easily be fixed at the fusion joints 5 without being cut.The part of the elastic member 4 that is fixed in the fusion joint 5 maybe merely held between the two sheet materials but with tightness so asnot to move between the two sheet materials or may have its surfacefusion bonded to one or both of the sheet materials. The grooves forpressing pressure reduction can be provided on either one or both of theprojections and facing surface.

After the fusion joints 5 are formed, the two sheet materials having theelastic members 4 therebetween are subjected to a uniting process forforming the end seals 11 along portions spaced apart in the elasticmembers 4 extending direction. The uniting process is accomplished byheat embossing or ultrasonic embossing. The uniting process may be aprocess in which an adhesive is applied to one or both of the two sheetmaterials and/or the elastic members and pressing the adhesive-appliedparts. When end seals 11 are not formed, the uniting process can beomitted.

The sheet materials 2 and 3 with the elastic members 4 therebetween isthen cut across so that the portions having been subjected to theuniting process may be positioned at both ends of the cut part in theelastic members 4 extending direction. The elastic members 4 are let tocontract to make each of the sheet materials 2 and 3 create folds. Theextensible composite member ID having the above-described configurationis thus obtained.

While the present invention has been described with particular referenceto its preferred embodiments, the present invention should not beconstrued as being limited thereto. Examples of alterations ormodifications are as follows.

While the folds in the extensible composite members 1 and 1′continuously run between the two elastic members positioned at both Ydirection ends, an elastic member at or near one or both of the Ydirection ends may be joined to the sheet materials 2 and 3. It ispreferred, nevertheless, that the folds runs to bridge across at leastthree, preferably a half, more preferably 70% or more, of the number ofthe elastic members. The end(s) of the elastic members 4 joined to thesheet materials 2 and 3 may be inboard of the X direction end(s) of theextensible composite member 1 instead of being at the end portion(s) ofthe extensible composite member 1.

In the third aspect of the invention, the number of the elastic membersof the extensible composite member does not need to be equal to thenumber of the joint lines in the elastic members extending direction (Xdirection). For example, FIG. 8 illustrates an extensible compositemember 1B, in which every elastic member 4 overlaps fusion joints 5forming a joint line in the elastic members 4 extending direction (Xdirection) but the elastic member 4 is disposed on every second jointline in the extending direction (X direction).

The extensible composite member of the third aspect may have elasticmembers 4B disposed not to overlap fusion joints, like an extensiblecomposite member 1C illustrated in FIG. 9, in addition to elasticmembers 4A disposed to overlap fusion joints. The elastic members 4B ofthe extensible composite member 1C shown in FIG. 9 are fixed to thesheet materials only at the ends seals 11 (only one of which isdepicted). It should be noted, however, that at least two of the elasticmembers disposed in the extensible composite member are fixed at thefusion joints. It is preferred that at least one-third, more preferablyat least a half, of the number of the elastic members disposed in theextensible composite member be fixed at the fusion joints. While, in theembodiment shown in FIG. 9, every second elastic member is fixed atfusion joints, every nth (n being a given number), e.g., third or fourthelastic member may be fixed. When both fusion joints having an elasticmember fixed therein and fusion joints having no elastic member fixedtherein are to be formed, the above-mentioned method of making theextensible composite member is carried out by using an embosser having agroove (depression) for pressing pressure reduction only on a part ofthe projections for fusion bonding or the surface facing the part of theprojections.

The fifth and sixth aspects of the present invention may be implementedas, for example, in the following embodiments.

The configuration in which the positions of joints vary between two ormore joint lines may be such that two joint lines Sa and Sb different inthe positions of joints alternate as in the embodiment illustrated inFIG. 12.

The pitch of the joints may vary between joint lines. The distancebetween adjacent joint lines does not need to be constant. The elasticmembers 4 do not need to be equally spaced. For instance, the extensiblecomposite member may have a group of elastic members spaced at arelatively small interval and a group of elastic members spaced at arelatively large interval, or the interval between adjacent joint linesmay be gradually or stepwise increased from one endmost elastic memberto the other endmost elastic member. In this way, by altering thearranging interval of the elastic members or the kind and/or stretchratio of the elastic members as desired, allocation of the contractionstress of the elastic members can be controlled as designed to providean article, such as a pull-on disposable diaper, with improvedperformance. In application to pull-on disposable diapers, while notillustrated in the drawing, the gathers provided below a waist gathercan be designed to exert a stronger contraction stress in an about 10 mmto 80 mm area thereof along the joint lines than in the other area. Adiaper so designed constricts the effective part of a wearer's body forpreventing the diaper from sliding down thereby providing an improvedbody fit.

As illustrated in FIGS. 14 and 15, the joints 5 composing each jointline S may be dispersed to some extent in the width direction of thejoint line. It is preferred, nevertheless, that the width L5 (see FIG.14) of the joint line S in the elastic members extending direction (Xdirection) be 1.0 to 50 times the length L13 of the individual joints 5in the elastic members extending direction (X direction). For instance,the width L5 of each joint line S may be 1.0 to 20 times, 1.0 to 10times, or 1.0 to 5 times, the length L13 of the individual joints 5. Thebreadth of dispersion of joints 5 in one joint line S (equal to thewidth of the joint line) is preferably not more than ¼, more preferablynot more than 1/20, the distance from the joint line to either ofadjacent joint lines. In the embodiment shown in FIG. 14, the joints ineach joint line are aligned in a staggered formation. In the embodimentshown in FIG. 15, the joints in each joint line are aligned in a wavyformation. Whichever of the patterns shown in FIGS. 13(a), 13(b), 14,and 15 the joints take on, there will be obtained the same action andeffect as with the extensible composite member 1D.

In the present invention inclusive of the first to sixth aspects, thenumber of the elastic members in an extensible composite member isdecided as appropriate to the dimension and use of the extensiblecomposite member. It is selected from, for example, a range of 5 to 30.The joints between the sheet materials formed by fusion bonding may bereplaced with those formed by adhering the sheet materials with, e.g., ahot-melt adhesive. The pattern of forming the fusion joints can bealtered as appropriate. The shape of the individual fusion joints isappropriately chosen from a rectangle, an elongated circle, a circle, adiamond, and so forth.

The extensible composite members according to the first, third, andfifth aspects of the present invention are especially suited to makeextensible portions of absorbent articles, such as disposable diapersand sanitary napkins. In these applications, a separately preparedextensible composite member may be fixed to an absorbent article toprovide an absorbent article having an extensible portion.Alternatively, the steps for making an extensible composite member maybe incorporated into the production line of an absorbent article toproduce an absorbent article having an extensible composite memberincorporated therein.

FIG. 4 illustrates extensible portions formed of extensible compositemembers, taking for instance a disposable diaper 20 with fastening tapes21. The extensible composite member of the present invention can be usedto make, for example, a waist extensible portion 22, a fasteningtape-neighboring extensible portion 23 that extends and contracts withthe fastening tape 21, a below-waist extensible portion 24, and anextensible portion 25 formed on the skin-contact side of a standinganti-leak cuff, and the like.

INDUSTRIAL APPLICABILITY

The extensible composite member according to the first aspect of theinvention has gathers (an extensible portion with many folds) soft tothe touch and beautiful to the eye, and provides an absorbent article,etc. with such gathers.

The method of making an extensible composite member according to thesecond aspect of the invention provides with ease an extensiblecomposite member having gathers (an extensible portion with many folds)soft to the touch and beautiful to the eye.

The extensible composite members according to the third and fifthaspects of the invention have gathers (an extensible portion with manyfolds) which are flexible, soft and smooth to the touch, and provide anabsorbent article, etc. with such gathers.

The methods of making an extensible composite member according to thefourth and sixth aspects of the invention provide with ease anextensible composite member having gathers (an extensible portion withmany folds) which are flexible, soft and smooth to the touch.

1. An extensible composite member having an extensible portioncomprising two sheet materials and a plurality of elastic membersintermediate between the sheet materials, the two sheet materials beingdiscontinuously bonded to each other at joints in the extendingdirection of the extensible portion and a direction perpendicular to theextending direction of the extensible portion, the elastic members beingarranged in the extensible portion avoiding the joints between the sheetmaterials and having both ends thereof fixed to the sheet materials,each of the two sheet materials forming a plurality of foldscontinuously running across a plurality of the elastic members.
 2. Theextensible composite member according to claim 1, wherein the jointsbetween the two sheet materials are formed by fusion bonding the sheetmaterials.
 3. The extensible composite member according to claim 1,Wherein the joints between the sheet materials are arranged in astaggered pattern, have a pitch P1 of 1 to 30 mm and each have a lengthL1 of 0.1 to 5 mm both measured in the extending direction of theextensible portion with the extensible portion being in the extendedstate, and the ratio of the pitch P1 to the length L1 (P1/L1) rangesfrom 1.1 to
 300. 4. The extensible composite member according to claim1, wherein the joints between the sheet materials are arranged to lineup in both the extending direction of the extensible portion and adirection perpendicular thereto, the joints lining in the perpendiculardirection are placed between every two adjacent elastic members, thejoints have a pitch P2 of 1 to 20 mm and each have a length L2 of 0.1 to5 mm both measured in the extending direction of the extensible portionwith the extensible portion being in the extended state, and the ratioof the pitch P2 to the length L2 (P2/L2) ranges from 1.1 to
 200. 5. Amethod of making the extensible composite member according to claim 1,comprising the steps of: arranging a plurality of elastic members intheir stretched state on a first sheet material and superposing a secondsheet material on the side of the first sheet material having theelastic members on, partly joining the first and second sheet materialsin their superposed state in an area where the elastic member is absent,subjecting the first and the second sheet materials with the elasticmembers therebetween to a process for fixing the elastic members to thefirst and the second sheet materials along portions spaced apart fromeach other in the extending direction of the elastic members, andallowing the elastic members to contract to cause each of the first andthe second sheet materials to form a plurality of folds.
 6. Anextensible composite member comprising two sheet materials and aplurality of elastic members intermediate between the sheet materials,the sheet materials being discontinuously bonded to each other in theextending direction of the elastic members and a direction perpendicularthereto to form a plurality of joint lines each composed of a pluralityof joints in each of the two directions, at least two of the elasticmembers being disposed along the joint lines in the extending directionto overlap each of the joints composing the respective joint lines andfixed between the sheet materials at the individual joints, and thesheet materials each forming folds between the joint lines in thedirection perpendicular to the extending direction.
 7. The extensiblecomposite member according to claim 6, wherein the joint lines in thedirection crossing the extending direction each have a ratio of a pitchP11 of arranging the fusion joints to a length L11 of the individualfusion joints (P11/L11) ranging from 1.05 to 80, and the pitch P11 ofarranging the fusion joints is 1 to 40 mm.
 8. The extensible compositemember according to claim 6, wherein the joints between the two sheetmaterials are formed by fusion bonding the sheet materials.
 9. A methodof making the extensible composite member according to claim 6,comprising the steps of disposing a plurality of elastic members intheir stretched state between two sheet materials and partlyheat-pressing the superposed sheet materials with a plurality ofprojections to partly fusion bond the sheet materials to form thejoints, the step of partly heat-pressing being carried out in a mannerthat does not result in cutting the elastic members.
 10. An extensiblecomposite member comprising two sheet materials and a plurality ofelastic members disposed between the sheet materials, the two sheetmaterials being partly bonded to each other to form joints, the jointslining up to make joint lines in a direction crossing the extendingdirection of the elastic members, a part of the joint lines and anotherpart of the joints being different in positions of the joints making upeach joint line in the direction crossing the extending direction, theelastic members being each fixed between the sheet materials at at leastpart of the joints, and the sheet materials each forming folds betweenevery two adjacent joint lines.
 11. The extensible composite memberaccording to claim 10, wherein the width of the joint line in theextending direction of the elastic members is 1.0 to 50 times the lengthof the individual joints in the extending direction of the elasticmembers.
 12. The extensible composite member according to claim 10,wherein the positions of the joints composing the individual joint linesin a crossing direction crossing the extending direction of the elasticmembers vary from one end to the other in the extending direction of theelastic members by a given distance in the crossing direction.
 13. Theextensible composite member according to claim 12, wherein the positionsof the joints composing the individual joint lines in a crossingdirection crossing the extending direction of the elastic members varyfrom one end to the other in the extending direction by a distancecorresponding to 3% to 50% of the pitch of the joints in the jointlines.
 14. The extensible composite member according to claim 10,wherein the ratio of the pitch P 11 of the fusion joints in theindividual joint lines to the length L11 of the individual fusion jointsin the joint lines (P11/L11) ranges from 1.05 to 80, and the pitch P11of the fusion joints is 1 to 40 mm.
 15. The extensible composite memberaccording to claim 10, wherein the joints are formed by fusion bondingthe two sheet materials.
 16. A method of making the extensible compositemember according to claim 10, comprising the steps of disposing aplurality of elastic members in their stretched state between two sheetmaterials and partly heat-pressing the superposed sheet materials with aplurality of projections to partly fusion bond the sheet materials toform the joints, the step of partly heat-pressing being carried out in amanner that does not result in cutting the elastic members.